The creator of Piano Hero, Nicholas Piegdon, has been sent a Cease and Desist letter from Activision, the publisher of the Guitar Hero games.
Activision asked that Nicholas stop using the name in regards to his game. Piano Hero is an open source game and due to Nicholas's lack of legal expertise in the area and "time, money, or energy", he has decided to comply with the request.
The entire letter from Activison and Nicholas's reply can be found at the link.
